Bottle cap

A plastic bottle cap on a water bottle

Beer bottle, with a Crown cork

Bottle caps are used to seal the opening of bottles. For glass bottles, these are usually small, specially adapted pieces of metal. With plastic bottles, plastic caps are used instead.

The original bottle cap was called Crown cork. It is pressed onto the bottle, and can be removed, using a bottle opener.

In recent years bottle caps with screw on mounts are used that way, a bottle opener is no longer required.